Shoring jacking

ABSTRACT

A jack is disclosed consisting of a piston and cylinder unit which can be expanded by introduction of compressed gas into the cylinder so as to engage two opposed surfaces to be shored. A rotatable collar is mounted on the end of the cylinder receiving the piston and is provided with inclined cam profiles which when rotated engage a pin located in a diametric pair of holes provided in the piston. The collar can be locked against rotation when the cam profiles are in engagement with the pin so as to prevent retraction of the piston and cylinder unit from the shored surfaces if pressure is lost or released from the cylinder.

1451 Dec. 3, 1974 SHORING JACKING [75] Inventor: Harry Berg, Abbotsford, British Columbia, Canada [73] Assignee: H. B. Contracting Ltd., Surrey,

British Columbia, Canada 22 Filed: May 25,1972

21 Appl. No.2 256,731

[52] US. Cl. 254/93 R, 61/41 A [51] Int. Cl B66f 3/24 [58] Field of Search 254/93 R, 133 A; 248/354 H, 354 P; 6l/41 A [56] References Cited UNITED STATES PATENTS 1,590,830 6/1926 Jewkes 254/93 R 2,691,503 10/1954 Bigelow 254/93 R 3,321,182 5/1967 Elenburg 254/93 R 3,393,521 7/1968 Cammisa 61 41 A 3,470,699 10/1969 Cox 61/41 A FOREIGN PATENTS OR APPLICATIONS 6/1965 France 61/41 A 564,597 12/1957 Italy ..248/354P Primary Examiner-Al Lawrence Smith Assistant Examiner-Robert C. Watson Attorney, Agent, or FirmFeatherstonhaugh & Co.

[ 5 7 ABSTRACT A jack is disclosed consisting of a piston and cylinder unit which can be expanded by introduction of compressed gas into the cylinder so as to engage two opposed surfaces to be shored. A rotatable collar is mounted on the end of the cylinder receiving the piston and is provided with inclined cam profiles which when rotated engage a pin located in a diametric pair of holes provided in the piston. The collar can be locked against rotation when the cam profiles are in engagement with the pin so as to prevent retraction of the piston and cylinder unit from the shored surfaces if pressure is lost or released from the cylinder.

6 Claims, 3 Drawing Figures PATENTELUEB 1851 56 SHORING J ACKING The invention relates to shoring jacks of the kind comprising a piston and cylinder, particularly for the use in shoring trench walls.

In the shoring of trenches, it is necessary to hold the shoring boards tightly against the wall of the trench so as to prevent sloughing of the material behind the boards. If the boards are allowed to shift even by the most minute amount, the soil'cohesion is lost and it is usually impossible to prevent sloughing and maintain a full safe trench width. The use of a simple piston and cylinder type jack for shoring purposes is not satisfactory since it tends to relax and allow the boards to move away from the trench wall. This in turn produces the undesirable sloughing referred to above.

It is among the objects of the present invention to provide an improved piston and cylinder type shoring jack in which this difficulty is overcome.

The invention therefore provides a shoring jack comprising a piston and cylinder unit for location between two surfaces to be shored, the cylinder of said unit having inlet means for connection to a pressure source for expanding the unit into engagement with said surfaces, a collar mounted for rotation on the end of said cylinder receiving said piston, said collar having an end extending axially from said cylinders to surround the piston and being formed with an inclined circumferentially extending cam profile, means for releasably securing the collar against rotation relative to the cylinder, a cam element, and means for selectively locating said cam element at one of a plurality of positions along said piston for cooperating engagement with the cam profile, whereby, subsequent to pressurization of the cylinder, the jack can be retained in the resulting expanded condition by securing the cam on the piston adjacent to the cam profile, rotating the collar to bring the cam profileinto abutment with the cam element, and securing the collar against rotation relative to the cylinder to prevent the cam profile from disengaging from the cam element.

One embodiment of the invention will now be described with reference to the accompanying drawings in which FIG. 1 is an exploded view of a jack according to the invention.

FIG. 2 is a perspective view of one element of the jack of FIG. 1 and,

FIG. 3 is a side elevation showing the jack of FIG. 1 assembled and in use in a trench.

Referring first to FIG. 1, the jack 1 is shown comprises a cylinder 2 having a bearing plate 3 closing one end and a gas inlet connector 4 secured in the cylinder wall close to the bearing plate. Vent holes 5 are provided in the wall of the cylinder 2 approximately three quarters of the length of the cylinders from the bearing plate 3. A piston 6 is similarly closed at one end by a bearing plate 3. At its other end, the piston 6 is closed by an end wall 7 to which a rubber sealing cup 8 is secured by a bolt 9 extending through a retainer disc 10. The piston 6 is tubular and along its length is formed with pairs of diammetrically opposed holes 11 in which a pin 12 may be located. The bearing plates 3 are each 6 provided with adjustable set screws 3a for engagement with the shoring boards when the jack is in use, to prevent slippage.

A cylindrical collar 13 is provided through which the piston 6 may be introduced into the cylinder 2. One end of the collar 13 has a portion 14 of enlarged diameter extending to a step 15, the end 16 of the cylinder 2 being a slip fit into the portion 14 to abut the step 15. A threaded boss 17 is provided in the wall of the portion 14, with a threaded stud 18 being engaged in this boss. The boss 18 carries a handle 19 whereby. the stud can be tightened into engagement with the cylinder 2 to prevent relative rotation of the collar 13 relative to the cylinder. The handle 19 also carries a flange 20 which retains one end of a chain 21. The pin 12 is secured to the other end of the chain 21. The other end of the collar 13, as best seen in FIG. 2, is formed with a pair of symmetrical inclined circumferential camming surfaces 22 each extending through substantially and each terminating in stop faces 23 and 24 at their upper and lower ends respectively.

The jack is assembled by introducing the piston 6 through the collar 13 in the position shown in FIG. 1 and so that the cup 8 enters the cylinder 2. The jack is then collapsed until the end of the cylinder 2 bears on the step 15 and the piston is fully received in the cylinder.

FIG. 3 shows the jack in position in a trench supporting shoring boards 25. In order to locate the jack in the trench, the inlet connector 4 is first connected to the source of compressed gas 26 which may for example be CO through a pressure pipe 27 having a valve 28 therein. Valve 28 is opened to introduce gas under pressure into the cylinder 2 so that the piston extends until the bearing plates 3 bear against the shoring 25. The set screws 3a bite into the wood of the shoring boards to prevent any vertical movement of the jack. 1

The pin 12, which serves as a camming element, is then inserted through the pair of diametric holes 11 in the piston 6 which are nearest to the stop surfaces 24 at the lower ends of the inclined cams 22 on the collar 13. The collar 13 is then rotated until the inclined cams 22 are in firm abutting engagement with the pin and the collar is then locked by rotating the handle 19 to engage the stud 18 with the cylinder 2. The stop faces 23 prevent the pin 12 from overriding the ends of the camming surfaces 22 during rotation of the collar 13. Pres- V sure can then be released from the cylinder 2 by closing the valve 28 and removing the connector 27. The jack is held in the extended position by the abutment of the pin 12 with the cam surfaces.

In order to prevent over extension of the jack, the vent holes 5 provided in the wall of the cylinder 2 vent the gas from the cylinder 2 as soon as the piston 6 is ejected from the cylinder sufficiently far for the cup 8 to pass beyond the holes 5. As a result, no further extension of the jack takes place.

I claim:

1. A pneumatic jack for use in the shoring of trenches, comprising a piston and cylinder unit having a port for separately operable mechanical means engageable between the piston and cylinder for the secural and retention thereof against retraction from a random expanded condition, wherein said mechanical means comprises a collar formed with an internal annular step and rotatably engaging the end of said cylinder receiving said piston, said collar having an end extending axially from said cylinder to surround the piston, said end being formed with a pair of inclined circumferential surface profiles, each extending through substantially 180,

an abutting element, and

means for selectively locating said abutting element at one of a plurality of positions along said piston for abutting engagement with said surface profiles,

means for preventing rotation of said collar relative to said cylinder,

whereby, subsequent to the pressurization of said cylinder for an extension of the unit to a final extended condition which applies a shoring force to opposed shoring boards lining the walls of a trench, the abutting element can be located on the piston adjacent to the surface profiles and the collar rotated to bring the surface profiles into abutting engagement with the abutting element without further extension of the unit, and then secured.

2. A pneumatic jack as claimed in claim 1, wherein said collar is formed with stop faces at each end of each of said surface profiles.

3. A pneumatic jack as claimed in claim 1, wherein said means for selectively locating said cam element comprise a plurality of axially spaced diametric holes formed in said piston, said abutting element comprising a pin engageable selectively in any of said holes.

4. A pneumatic jack as claimed in claim 1, wherein said cylinder is formed with a plurality of circumferentially spaced vent holes to prevent extension of the jack beyond a predetermined amount 5. A pneumatic jack as claimed in claim 1 wherein the piston and cylinder unit is provided with a bearing plate at each end, each of said bearing plates including means for penetrative engagement with said shoring boards.

6. A pneumatic jack for use in the shoring of trenches, comprising a cylinder having a bearing plate at a closed first end for engagement with a shoring board lining a wall of a trench to be shored, and a port for the introduction and release of gas under pressure,

valve means connected to said port,

a piston having another bearing plate at a first end for engagement with another shoring board lining an opposite wall of the trench to be shored, and a sealing cup secured at a second end which is received in the open second end of the cylinder, said piston being further provided with a plurality of axially spaced pairs of diametric holes,

said bearing plates being formed with threaded apertures each receiving axially adjustable set screws for penetrative engagement with said shoring boards,

a collar formed with a threaded radial aperture, and having an internal step engaging the second end of said cylinder, said collar being rotatable with respect to said cylinder, and having an axially extending end surrounding said piston and formed with a pair of symmetrical surface profiles each extending through substantially a threaded stud provided with a handle and engaging in said threaded radial aperture in said collar for releasably securing the collar against rotation relative to said cylinder, and

a pin engageable selectively in one of said pairs of diametric holes in the piston,

whereby, subsequent to pressurization of the cylinder to cause the bearing plates and set screws to engage the shoring boards, the piston and cylinder can be secured in the resulting extended condition and the valve means operated to release the gas under pressure after locating the pin in a pair of said holes ad jacent to the surface profiles, rotating the collar to bring the surface profiles into abutment with the pin without further extending the piston and cylinder, and securing the collar against rotation by tightening the threaded stud against the cylinder so as to prevent the surface profiles from disengaging from the pin.

UNITED STATES PATENT AND TRADEMARK OFFICE CERTIFICATE OF CORRECTION PATENT'NO. 3,851,856

DATED 3 December 3, 1974 INVENTOR( 3 Harry Berg It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

Figures 1 and 2, reference numeral 18 should be added to indicate the stud which carries handle 19, this stud being threaded into threaded boss 1?.

Column 1, line 28, "cylinders" should read "cylinder".

Column 1, line 57, "cylinders" should read "cylinder".

Column 2, line 8, "boss 18" should read "stud l8".

Claim 1, line 3 should read: --a piston and cylinder unit having a port for the introduction and release of gas under pressure,-.

Signed and Scaled this Twenty-fifth Day of September I 979 [SEAL] Arrest:

LUTRELLE F. PARKER Arresting Officer Acting Commissioner of Patents and Trademarks 

1. A pneumatic jack for use in the shoring of trenches, comprising a piston and cylinder unit having a port for separately operable mechanical means engageable between the piston and cylinder for the secural and retention thereof against retraction from a random expanded condition, wherein said mechanical means comprises a collar formed with an internal annular step and rotatably engaging the end of said cylinder receiving said piston, said collar having an end extending axially from said cylinder to surround the piston, said end being formed with a pair of inclined circumferential surFace profiles, each extending through substantially 180*, an abutting element, and means for selectively locating said abutting element at one of a plurality of positions along said piston for abutting engagement with said surface profiles, means for preventing rotation of said collar relative to said cylinder, whereby, subsequent to the pressurization of said cylinder for an extension of the unit to a final extended condition which applies a shoring force to opposed shoring boards lining the walls of a trench, the abutting element can be located on the piston adjacent to the surface profiles and the collar rotated to bring the surface profiles into abutting engagement with the abutting element without further extension of the unit, and then secured.
 2. A pneumatic jack as claimed in claim 1, wherein said collar is formed with stop faces at each end of each of said surface profiles.
 3. A pneumatic jack as claimed in claim 1, wherein said means for selectively locating said cam element comprise a plurality of axially spaced diametric holes formed in said piston, said abutting element comprising a pin engageable selectively in any of said holes.
 4. A pneumatic jack as claimed in claim 1, wherein said cylinder is formed with a plurality of circumferentially spaced vent holes to prevent extension of the jack beyond a predetermined amount.
 5. A pneumatic jack as claimed in claim 1 wherein the piston and cylinder unit is provided with a bearing plate at each end, each of said bearing plates including means for penetrative engagement with said shoring boards.
 6. A pneumatic jack for use in the shoring of trenches, comprising a cylinder having a bearing plate at a closed first end for engagement with a shoring board lining a wall of a trench to be shored, and a port for the introduction and release of gas under pressure, valve means connected to said port, a piston having another bearing plate at a first end for engagement with another shoring board lining an opposite wall of the trench to be shored, and a sealing cup secured at a second end which is received in the open second end of the cylinder, said piston being further provided with a plurality of axially spaced pairs of diametric holes, said bearing plates being formed with threaded apertures each receiving axially adjustable set screws for penetrative engagement with said shoring boards, a collar formed with a threaded radial aperture, and having an internal step engaging the second end of said cylinder, said collar being rotatable with respect to said cylinder, and having an axially extending end surrounding said piston and formed with a pair of symmetrical surface profiles each extending through substantially 180*, a threaded stud provided with a handle and engaging in said threaded radial aperture in said collar for releasably securing the collar against rotation relative to said cylinder, and a pin engageable selectively in one of said pairs of diametric holes in the piston, whereby, subsequent to pressurization of the cylinder to cause the bearing plates and set screws to engage the shoring boards, the piston and cylinder can be secured in the resulting extended condition and the valve means operated to release the gas under pressure after locating the pin in a pair of said holes adjacent to the surface profiles, rotating the collar to bring the surface profiles into abutment with the pin without further extending the piston and cylinder, and securing the collar against rotation by tightening the threaded stud against the cylinder so as to prevent the surface profiles from disengaging from the pin. 